ORTHOMINASRAGRITE, V4+O (SO4) (H2O)5, A NEW MINERAL SP

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• journal_title：The Canadian Mineralogist
• Contributor：Frank C. Hawthorne ; Michael Schindler ; Joel D. Grice ; Patrick Haynes
• Publisher：Mineralogical Association of Canada
• Date：2001-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.39.5.1325
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：39
• issue：5
• firstpage：1325
• section：Articles

摘要

<p id="p-1">Orthominasragrite, Vp>4+p>O (SO₄) (H₂O)₅, is a new mineral species from Temple Mountain, Emery County, Utah. It occurs as rounded aggregates (up to ~200 μm across) of irregular grains that are pale blue to bright blue, depending on size. Orthominasragrite has a pale blue streak, a vitreous luster, and no observable fluorescence under ultraviolet light. It has no cleavage or parting. The Mohs hardness is ~1, and the calculated density is 2.00 g/cmp>3p>. Orthominasragrite is biaxial negative (pseudo-uniaxial) with α 1.529(2), β 1.534(2), γ 1.534(2), 2m>Vm>_obs = 2(4)°, 2m>Vm>_calc = 0°, non-pleochroic, m>Xm> = m>bm>, m>Ym> = m>c, Zm> = m>am>. Orthominasragrite is orthorhombic, space group m>Pmnm>2₁, m>am> 7.246(4), m>bm> 9.333(6), m>cm> 6.210(4) Å, m>Vm> 420.0(3) Åp>3p>, m>Zm> = 2. The strongest seven lines in the X-ray powder-diffraction pattern [m>dm> in Å(m>Im>)(m>hklm>)] are as follows: 4.699(10)(101,020), 3.322(5)(121), 2.865(4)(220), 2.602(3)(221,131,022), 3.734(2)(021), 3.622(2)(200), and 3.108(2)(002). Chemical analysis by electron microprobe gave VO₂ 33.88, SO₃ 31.97, H₂O (calc.) 36.30, sum 102.15 wt.%; the proportion of H₂O was determined by crystal-structure analysis. The resulting empirical formula on the basis of 10 anions (including 5 H₂O) is V_1.014 S_0.991 O₅ (H₂O)₅; the end-member formula is VO (SO₄) (H₂O)₅. Orthominasragrite is the orthorhombic form of (monoclinic) minasragrite. The crystal structure was solved by direct methods and refined to an m>Rm> index of 4.4% for 1007 observed (|m>Fm>_o| > 5σm>Fm>) reflections measured with an automated four-circle X-ray diffractometer using Mom>Km>α X-radiation. There is one m>Vm> site occupied by Vp>4+p> and surrounded by one O atom and 5 (H₂O) groups in an octahedral arrangement, with one short apical vanadyl bond (1.580 Å), four similar equatorial bonds (<2.026 Å>), and one longer V–O bond (2.231 Å) m>transm> to the vanadyl bond. The structure consists of isolated (Vp>4+p>ϕ₆) octahedra (ϕ: unspecified anion) and (SO₄) tetrahedra linked by hydrogen bonds. p>